Pathology diagnostic investigation of patient material (tissue and cells) is the basis of many treatment decisions, in particular in oncology. Usually, thin slices from a biopsy are presented on microscope slides and stained according to certain protocols. Specific stains are used for scoring and grading the possibly present type of cancer. As the number of stains applied to a single slide is rather limited due to overlapping frequencies in the visual spectrum (especially in bright field microscopy), consecutive slices are used, each differently stained. In traditional pathology, the information of one slide is transferred to the next slide only in a figurative sense. Quickly alternating between multiple slides is impossible, as it requires to switch the physical slides and to find the region of interest. Therefore, registration of multiple slides has to be done in one's head by the operator (e.g. a pathologist).
With the introduction of digital scanners, image analysis tools may help the pathologists to register the (consecutive) slides. However, general registration techniques as global registration may not work due to differences in the tissue, deformation of the tissue, stretching of the tissue, etc. More advanced registration techniques such as local registration do not require a single (global) transformation matrix and permit local adaptation.